The use of thermal therapy (hyperthermia or hypothermia) for minimally- invasive surgery is facilitated by the ability to deliver large and varied doses of thermal energy virtually anywhere in the body via small diameter catheter based tools. While this technique holds incredible potential for minimizing surgical trauma, recovery time, and associated health care costs, it has fallen short of is potential in part due to a difficulty in monitoring the tissue damage front created by the therapy. This is particularly true of laser induced hyperthermia which we consider here. While techniques for acquiring this information using magnetic resonance imaging (MRI) have been explored, an adequate closed-loop control system has not yet been developed. We believe that currently the capability to collect this information with appropriate temporal, spatial, and temperature resolution exists and that creating a closed- loop feed-back thermal therapy system is a matter of appropriate hardware interface and control strategy. This project will develop a prototype for a computer system capable of real-time feedback control and visualization of thermal therapies. The system will interface a clinical Nd:YAG laser to an MRI console. Initially, this interface will be designed for a specific (TecMag) MRI console but will be adaptable to other MR systems as well as other thermal therapy tools. PROPOSED COMMERCIAL APPLICATIONS: This direct result of this research will be an interactive, image-guided, computer-controlled thermal therapy system which interfaces an existing magnetic resonance imaging system to a medical laser. It will allow a user to interactively specify a thermal profile which will then be generated by appropriate delivery of laser energy. This device will allow minimally invasive laser therapy of deep tissues to become reality thus greatly reducing health care costs by decreasing surgical trauma and recovery time. There are some 5000 clinical MRI scanners in the US currently and open MR scanners are becoming increasingly popular, thus the potential market for a commercially developed, MRI-ready thermal therapy system should met or exceed several thousand units. In addition, the interactive, closed-loop control system which will be developed in this project will be useful in any application where non-invasive monitoring and control of temperature profiles is required including ultrasound, microwave, and radio-frequency hyperthermia as well as cryotherapies.